1. Field of the Invention
The present invention relates to combustors for gas turbines, and in particular, to a pneumatic means for controlling flow distribution in such combustor.
2. Description of the Prior Art
Conventional combustors or combustion chambers in a gas turbine are designed to operate most efficiently at a particular power level, normally the power level at which the turbine is generally operated. At this power level the fuel injectors provide a given amount of fuel for mixing with a given volume of air or combustion-generating gas to provide the optimum fuel-air ratio.
A turbine, however, requires less power during start and idle. Such reduced power levels generally are achieved by reducing the fuel flow into the combustor. With a constant air supply, the fuel-air ratio during start and idle is leaner than optimum. This may result in unstable burning. While mechanical means for controlling air flow into a combustor during start and idle may be used, the complexity of such devices and the temperature environment in which they must operate have rendered them undesirable.
Accordingly, it is an object of this invention to provide a pneumatic means for limiting air flow into a combustor during start and idle thereby maintaining optimum fuel-air ratio while avoiding the disadvantages of mechanical means for controlling air flow.